1. Field of the Invention
This invention is related to the field of starter clutches for internal combustion engines and in particular to a thrust ring for a starter clutch.
2. Description of the Prior Art
Starter clutches for internal combustion engines of the type taught by Digby in U.S. Pat. Nos. 3,263,509, by Losey in 4,712,435 and by Giometti in 4,715,239 have enjoyed wide acceptance in the automotive industries of the world. These starter clutches employ a plurality of flyweights disposed within a driven member which are radially displaced as a function of the rotational speed of the driven member. The flyweights have included cam surfaces which engage a conical surface of a thrust ring such that the radial displacement of the flyweights produces an axial displacement of the thrust ring. The thrust ring abuts a driving member of the starter clutch which is resiliently biased into engagement with the driven member. When the rotational speed of the driven member exceeds a predetermined speed, the flyweights axially displace the thrust ring which in turn axially displaces the driving member a distance sufficient to disengage the ratchet teeth of the driving member from the ratchet teeth of the driven member.
This flyweight-thrust ring combination is utilized to eliminate severe wear on the ratchet teeth of the clutch when the driven member is rotating faster than the drive member. Additionally, the combination eliminates the noise associated with the chattering of the ratchet teeth that would otherwise accompany overspeeding of the driven member relative to the drive member.
In the clutches disclosed in the above referenced patents, the annular thrust ring is a machined part having a radial face which engages the drive member and an internal conical surface which engages the inclined cam surfaces on the flyweights. The radial and conical surfaces of the thrust ring must be machined to relatively close dimensional tolerances and have a relatively smooth surface finish in order to minimize wear and achieve a satisfactory service life.